DC2, either a wall adapter hooked to that USB cable, or a SEPARATE "powered" USB hub (i.e. not hooked to your computer).
My computer repair guy has a whole shelf of laptops and computers with dead motherboards and blown USB ports due to people charging things on their PCs. He taught me not to do it.
Most of us have many devices (cell phones, bluetooth devices like speakers, vape gear) all needing to be charged, I have a charging station set up on a portion of my kitchen counter with a stand-alone USB port where they all get *fed*.
I highly recommend NOT charging thru your PC. It's sort of the same as telling people not to charge things overnight.....many laugh at that and do it anyway, but stuff happens.
Powered means it gets it charge from something other than your PC, i.e. a wall socket.
http://lifehacker.com/five-best-usb-hubs-1414094277
http://usb-hub-review.toptenreviews.com/
http://thewirecutter.com/reviews/best-usb-hubs/
We're talking $20-$50 versus $300-$1200 for a computer.
On similar subject, using cheapo usb car chargers also a bad idea. They rarely deliver steady and/or proper voltage. And if you get a dud, like I did, it blew the electrical fuses in my truck.
Hey DC2, glad to help, it seems like yesterday you taught me how to use a dripping atomizer way back in 2012.

Amazing isn't it? It seemed rather confusing at the time and of course, the gear was pretty different back then.........but it all still works great!!!!